From 20bf82a898b65c129af76deb96a1b415d3098a28 Mon Sep 17 00:00:00 2001
From: Josef Bacik <josef@toxicpanda.com>
Date: Fri, 15 Nov 2024 10:30:28 -0500
Subject: [PATCH] mm: don't allow huge faults for files with pre content
watches
There's nothing stopping us from supporting this, we could simply pass
the order into the helper and emit the proper length. However currently
there's no tests to validate this works properly, so disable it until
there's a desire to support this along with the appropriate tests.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/9035b82cff08a3801cef3d06bbf2778b2e5a4dba.1731684329.git.josef@toxicpanda.com
---
mm/memory.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/mm/memory.c b/mm/memory.c
index 75c2dfd04f725..32e20f41ed208 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -76,6 +76,7 @@
#include <linux/ptrace.h>
#include <linux/vmalloc.h>
#include <linux/sched/sysctl.h>
+#include <linux/fsnotify.h>
#include <trace/events/kmem.h>
@@ -5662,8 +5663,17 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
static inline vm_fault_t create_huge_pmd(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
+
if (vma_is_anonymous(vma))
return do_huge_pmd_anonymous_page(vmf);
+ /*
+ * Currently we just emit PAGE_SIZE for our fault events, so don't allow
+ * a huge fault if we have a pre content watch on this file. This would
+ * be trivial to support, but there would need to be tests to ensure
+ * this works properly and those don't exist currently.
+ */
+ if (unlikely(FMODE_FSNOTIFY_HSM(vma->vm_file->f_mode)))
+ return VM_FAULT_FALLBACK;
if (vma->vm_ops->huge_fault)
return vma->vm_ops->huge_fault(vmf, PMD_ORDER);
return VM_FAULT_FALLBACK;
@@ -5687,6 +5697,9 @@ static inline vm_fault_t wp_huge_pmd(struct vm_fault *vmf)
}
if (vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) {
+ /* See comment in create_huge_pmd. */
+ if (unlikely(FMODE_FSNOTIFY_HSM(vma->vm_file->f_mode)))
+ goto split;
if (vma->vm_ops->huge_fault) {
ret = vma->vm_ops->huge_fault(vmf, PMD_ORDER);
if (!(ret & VM_FAULT_FALLBACK))
@@ -5709,6 +5722,9 @@ static vm_fault_t create_huge_pud(struct vm_fault *vmf)
/* No support for anonymous transparent PUD pages yet */
if (vma_is_anonymous(vma))
return VM_FAULT_FALLBACK;
+ /* See comment in create_huge_pmd. */
+ if (unlikely(FMODE_FSNOTIFY_HSM(vma->vm_file->f_mode)))
+ return VM_FAULT_FALLBACK;
if (vma->vm_ops->huge_fault)
return vma->vm_ops->huge_fault(vmf, PUD_ORDER);
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
@@ -5726,6 +5742,9 @@ static vm_fault_t wp_huge_pud(struct vm_fault *vmf, pud_t orig_pud)
if (vma_is_anonymous(vma))
goto split;
if (vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) {
+ /* See comment in create_huge_pmd. */
+ if (unlikely(FMODE_FSNOTIFY_HSM(vma->vm_file->f_mode)))
+ goto split;
if (vma->vm_ops->huge_fault) {
ret = vma->vm_ops->huge_fault(vmf, PUD_ORDER);
if (!(ret & VM_FAULT_FALLBACK))
--
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